Silicon nitride has been used in wear and high temperature applications such as bearings and valves for internal combustion engines.
JP Published Patent Application No. (Kokai) 6-172034 reports that adding titanium carbide (TiC) to a silicon nitride green body imparts a black color to the densified silicon nitride material. As the color of a conventional densified silicon nitride material can be various shades of gray, the coloring achieved by adding TiC provides the desirable visual appearance of a more uniform, more consistent material. The average particle size of the TiC powder reported in JP 6-172034 was about one micron. Replication of one of the Examples therein produced a silicon nitride material whose maximum detectable TiC grain size was over 5.5 um, and whose D.sub.50 TiC grain size was about 1.36 um.
One commercial silicon nitride bearing material also contains a small amount of TiC. Analysis of a 75 mm.sup.2 polished microstructure of this material reveals that its largest detectable TiC grain was about 5.25 um, and its D.sub.50 TiC grain size was about 0.793 um.